The glutathione S-transferases appear to have three functions: They serve as catalysts in reactions in which glutathione is used to attack a vast number of compounds with a susceptible electrophilic atom; they serve as binding proteins for an even larger number of compounds that include bilirubin and heme; they serve as one of the reactants in the formation of covalent complexes with very highly reactive reagents including those with carcinogenic activity. All three functions have been investigated but that of catalysis has been emphasized. BIBLIOGRAPHIC REFERENCES: Benson, A.M., Talalay, P., Keen, J.H., and Jakoby, W.B.: Relationship between the soluble glutathione-dependent delta 5-3-ketosteroid isomerase and the glutathione S-transferases of the liver. Proc. Nat. Acad. Sci., USA 74: 158-162, 1977. Jakoby, W.B.: The glutathione S-transferases: A group of multifunctional detoxification proteins. Adv. Enzymol. 46: 381-412, 1977.